Cauliflower Au Gratin

Creamy Cauliflower Au Gratin in a casserole dish.

As healthy and rice-able as cauliflower is, it can also be rich and decadent.  This Cauliflower Au Gratin definitely leans toward the latter with a rich, slightly smoky mornay sauce spiked with whole grain dijon mustard for a little tang. #doesntsuck.

butter, flour and spice in a pan
bechamel sauce and whisk

This classic au gratin starts with a béchamel, enhanced with a few pantry staples to amp up the flavor.

adding cheese to béchamel

Tangy cheddar and smoked gouda transform the béchamel to a gloriously creamy, lush sauce.

steamed cauliflower
Cauliflower Mustard Au Gratin ready to bake.

Steam the cauliflower until it’s just tender and transfer to a baking dish.  Pour the cheese sauce over the cauliflower. Sprinkle with cheddar cheese and breadcrumbs to develop a good crust and bake.

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crumb coated cauliflower mustard au gratin hot from the oven.

Those golden, crispy crumbs on top can barely mask the cheesy-gooey interior of this casserole.

spooning out the gratin onto a dish.

When you tuck your spoon into the mix, and get a whiff of that rich mornay you’ll get a sense of the treat that you’re in for — tender cauliflower in a creamy, cheesy, tangy sauce that oozes across the plate.  This is a great side dish to roast meats or pan sautéed seafood — and if you’re looking for Thanksgiving inspiration, this is it.

A serving of cauliflower on a plate.

More cauliflower recipes you’ll love:

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Serving the cauliflower au gratin with a spoon.
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4.54 from 13 votes

Cauliflower Au Gratin

A rich, indulgent gratin with a cheesy, mustard-spiked mornay sauce that’s perfect for entertaining and the holidays.
Author: Lisa Lotts
Course Side Dish
Cuisine American
Keyword casserole, cauliflower, side dish
Dietary Restrictions Vegetarian
Prep Time 20 minutes
Cook Time 20 minutes
Total Time 40 minutes
Servings 6


  • 1 head cauliflower
  • 2 ½ tablespoons unsalted butter
  • tablespoons all purpose flour
  • ¼ teaspoon nutmeg
  • ¾ teaspoon dry mustard
  • pinch cayenne pepper
  • 1 teaspoon kosher salt
  • ½ teaspoon black pepper
  • 2 cups milk
  • 1 cup cheddar cheese grated, divided
  • ½ cup smoked gouda grated
  • 2 teaspoons whole grain dijon mustard
  • ¼ cup panko or breadcrumbs


  • Preheat the oven to 375°.  Spray a small casserole dish with vegetable spray and set aside.
  • Trim the end from the cauliflower and cut it vertically into 1″ slabs.  Trim the florets from the stem and then cut the stem into bite sized pieces.  Add about ½” water to a large pot and fit it with a steamer basket.  Bring the water to a boil and place the cauliflower into the basket.  Steam for about 10 minutes or until tender.  Set aside.
  • In a medium saucepan, heat the butter over medium high heat.  When butter is melted and bubbly, whisk in the flour, nutmeg, dry mustard, cayenne pepper, kosher salt and black pepper.  Stir until the butter and dry ingredients form a paste or roux.  Slowly add the milk, whisking constantly.  Cook, stirring and scraping the sides and edges until the milk mixture thickens and comes to a low boil.  Cook for one minute and remove from heat.
  • Add ¾ cup cheddar cheese and ½ cup gouda, stir until cheese is melted.  Stir in the whole grain dijon and set aside.
  • Spoon ¼ cup cheese sauce into the bottom of the casserole and spread evenly.  Use a slotted spoon to transfer the cauliflower to the casserole and arrange in an even layer.  Top with cheese sauce.  Sprinkle on the remaining cheddar cheese and bread crumbs.
  • Bake for 18-20 minutes until bubbly, then turn on the broiler to high and cook for 1-2 more minutes or until  breadcrumbs are nicely browned.  Remove from oven and rest for 5-10 minutes before serving.


Reheat leftovers in an oven at  350° for 10-15 minutes.


Calories: 273kcal | Carbohydrates: 13g | Protein: 14g | Fat: 18g | Saturated Fat: 11g | Cholesterol: 59mg | Sodium: 741mg | Potassium: 432mg | Fiber: 2g | Sugar: 6g | Vitamin A: 560IU | Vitamin C: 46.2mg | Calcium: 369mg | Iron: 0.8mg

Pin “Cauliflower Mustard Au Gratin”

This easy cauliflower casserole w/ two kinds of cheese and tangy dijon mustard is a great vegetarian side dish! Make Cauliflower Mustard Au Gratin tonight! #cauliflower #cauliflowerrecipes #vegetarianrecipes

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  1. 5 stars
    This is an easy recipe with TONS of flavors. Thank you!

  2. 5 stars
    I LOVE mustard with cauliflower! Keep up the good work!

  3. YUM. Holy smokes this looks and sounds amazing. You can call it a gratin. You can call it cauliflower cheese. I call it I need this in my mouth, STAT! Cauliflower is one of my favorite vegetables. I can’t wait to try this!

    1. I’m glad you approve Christina — it doesn’t last long in this house!

  4. 5 stars
    Whoa! How delicious. Love how you’ve added mustard into the sauce.

  5. 5 stars
    This is essentially a variation on what I know more humbly as cauliflower cheese, a staple especially for kids in the UK – this is a little fancier though and love the smoked gouda. By the way try it alongside steak – a great match!

    1. Anything with a béchamel in French is a gratin – sounds fancy, but it’s really just cauliflower cheese! LOL!

  6. OMG, this looks amazing! I’ve always been obsessed with cauliflower and I’m so glad everyone is embracing it these days. This is total comfort food!

    1. Thank you, Jenn! This IS comfort food… Enjoy!

  7. 5 stars
    I’m always on the lookout for ways I might be able to convince my husband to eat some cauliflower – smothering it in delicious cheese like this sounds like a pretty good bet! I especially love the Gouda!